Windows constructed from multiple glass panes utilized "muntins" or "muntin bars" to secure the edges of the individual glass panes within the window sash. In many windows, muntins formed distinctive grid patterns which became associated with architectural styles of buildings containing the windows.
Modern windows formed by insulating glass units utilize single glass lights separated by an insulating dead air space. Where a particular architectural "look" is desired, a grid of muntin bars is fixed in the dead air space between the glass lights to simulate a multipane window. Typical muntin bars for insulating glass units are formed from decoratively coated interfitted metal tubes. The grids are anchored to the insulating glass unit periphery.
Constructing muntin bar grids for insulating glass units has been a labor intensive process. As a consequence, manufacturing such units, and thus windows formed by the units, has been costly and inefficient. Some efforts to mechanize the manufacture of muntin grids have been made. For example, machines for notching lengths of preformed tubular muntin bar stock at predetermined locations have been proposed. The muntin bar stock is cut into lengths for use in forming a grid for a given size insulating glass unit. The cut muntin bar stock is then fed into the notching machine and notches are formed at predetermined locations along each length. The grids are assembled by hand by interfitting the respective muntin bars at the notches.
The muntin bar stock is produced by roll forming decoratively coated sheet material such as aluminum or steel, in a known manner. Various sizes of the sheet material are used to form different size muntin bar stock. The roll forming machine has a series of rolls configured to form sheet material into elongated tubular muntin bar stock. A window manufacturer purchases the muntin bar stock size(s) needed to produce insulating glass units and, as described above, cuts the stock into lengths that are notched and assembled into grids for incorporation into the insulating glass units.
Conventional muntin bar constructions suffer from several drawbacks with respect to cost and efficiency. For example, insulating glass unit manufacturers are required to purchase and maintain an inventory of tubular muntin bar stock. In some instances, several different muntin bar stock sizes and colors are inventoried to produce grids for various insulating glass units. This necessitates dedicated muntin bar stock storage space and increases costs associated with inventory. In addition, the muntin bar stock must be cut into lengths the size of which depends on the size of the insulating glass units being manufactured. While dedicated machinery may be used to cut the stock, a machine operator is still required to perform at least some hand measurements in order to produce correctly cut-to-length muntin bars. Moreover, cutting the muntin bar stock frequently results in unusable scrap.
The cut-to-length muntin bars are then fed to a notching device to form notches that will be located at the muntin bar intersections. Although some machinery may be specialized to notch the bars for forming grids, a number of hand measurements typically must be made so as to produce correctly sized muntin bars with properly located notches. As a result, conventional construction of muntin bars and muntin bar grids requires the operator to perform a series of complicated measuring and fabricating steps, thereby increasing the difficulty and cost associated with such construction. The handling and notching procedures may also adversely affect the appearance of the muntin bar by damaging the muntin bar finish and denting or creasing the bar.
The present invention provides a new and improved system for fabricating muntin bars which is so constructed and arranged that stock sheet material is quickly and efficiently formed into individual muntin bars that include notches, or other structure, to permit the bars to be subsequently attached to form a grid, without requiring significant handling or mentation on the part of the individual fabricating the muntin bars. The invention provides a method and apparatus for continuously producing notched muntin bars from stock material; thus, a manufacturer is able to store coils of stock material rather than a supply of precut tubular muntin stock. Also, production of the muntin bars is automatically controlled to allow muntin bars to be custom formed for specific orders.